The fifth overall draft pick will start at cornerback when the Cardinals open the season Sunday against the Carolina Panthers. Coach Ken Whisenhunt likes to bring rookies along more slowly but a season-ending knee injury to starter Greg Toler forced his hand.

Peterson will start alongside second-year pro A.J. Jefferson, who was on Arizona’s practice squad last year, giving the Cardinals an exceedingly young pair of cornerbacks.

“I haven’t figured it out yet, because if you’ve got old guys you get criticized for having old guys. If you’ve got young guys you get criticized for having young guys,” a somewhat defensive Whisenhunt said after the team practiced in triple-digit heat Wednesday. “Maybe we can go out and spend enough money under the cap and get the top player at every position and then we’d be OK.

“You know, at some point, young guys have got to play.”

Peterson said he did not expect to start this soon “because coach told me from the beginning he kind of wanted to spoon feed me because it’s definitely different from college.”

“I’ve got to grow up fast now,” he said. “I’ve got to grow up on the fly. But it’s going to be a fun opportunity. I can’t wait to go out there and really, really showcase my talents.”

Peterson showcased that talent in the preseason game against Green Bay, when he intercepted Aaron Rogers’ pass and returned it 34 yards for a touchdown. In addition to playing cornerback, he has won the punt returner’s job.

“The kid’s talented,” defensive coordinator Ray Horton said. “He’s made plays in the preseason, and that’s what we drafted him for. There’s a learning curve and it was accelerated by the injury to Greg, so No. 21’s going to be out there starting the game.”

Peterson will be facing a familiar foe in Carolina rookie quarterback Cam Newton, the No. 1 overall pick in the draft who will start for the Panthers.

They were SEC opponents when Peterson was at LSU and Newton at Auburn.

“Me and Cam, we have a lot of history together,” Peterson said, “going to almost every awards show together, almost every scene. Cam, he’s a great guy. I can’t wait to see him Sunday, see what he’s going to do. Hopefully, I can pick him off a couple of times.”

Auburn beat Peterson’s Tigers 24-17 last season en route to the national championship.

“He only had to throw five passes against us. He was running all over us,” Peterson said, “so me and him didn’t have too much of a clash.”

Opponents, Newton included, will undoubtedly look to take advantage of Arizona’s young corners.

“We hope so,” Peterson said. “We want them to take advantage, so we can go ahead and pick them off. Me and AJ, we have a tremendous amount of confidence within each other, this being our first career starts as young guys. It’s going to be fun for both of us. We’re both looking to make plays on Sunday and throughout the season.”